1. Field of the Invention
This invention relates to a conductive organopolysiloxane composition that can provide upon curing a conductive silicone rubber exhibiting a resistivity stable in conducting regions.
2. Description of the Prior Art
Silicone rubber compositions provide, upon curing, silicone rubbers having superior weatherability, heat resistance, freeze resistance, electrical insulation properties and so forth. Hence, making the most of such properties, they are used in various industrial fields. Various additives are also added to such compositions so that, after being cured, they can be used as conductive silicone rubbers. In such an instance, conductive carbon black is widely used as a conductive material. Since, however, carbon black blackens the compositions, it can not be used when products are not desired to be blackened.
In instances where an electrical conductivity of 1.times.10.sup.-2 .OMEGA..multidot.cm or below as volume resistivity is required, the conductive carbon black must be added in so large a quantity as to cause color migration to other portions.
In order to cope with such instances where products are not desired to be blackened or a low electrical resistance is required, studies are made on conductive materials other than carbon black. For example, studied are conductive metal powders such as gold powder, silver powder and nickel powder, and fillers such as glass beads which have been surface-treated with conductive metals to obtain fillers coated with conductive metals.
However, silicone rubbers compounded with conductive metal powders or glass beads coated with conductive metals still have an insufficient electrical conductivity and also have a disadvantage that they may undergo a change in electrical conductivity with time especially in a high-temperature environment of 100.degree. C. or above.
EP 653463 A discloses an electrically conductive silicone rubber composition containing a silver powder having low ammonium ion and sulphate ion concentrations and having reduced change in curability during ageing.
Japanese Patent Publication (kokai) 57-8249 discloses a composition, which is curable to give a rubbery elastomer, comprising a polyorganopolysiloxane, a polyorganohydrogenpolysiloxane, a transition metal powder and a catalyst.